1. Field of the Invention
This invention relates to a stencil making apparatus and a stencil making method, and more particularly to an apparatus and a method which make a perforated stencil sheet, based on data read from an original.
2. Description of the Related Art
For example, in a digital stencil printer with a stencil making apparatus, an original is read with reading means, and based on the read data, a perforated stencil sheet is made with stencil making means. The perforated stencil sheet is wound around the outer peripheral surface of a printing drum in a printing section, and this printing drum is driven to rotate. Between the printing drum and a press roller which rotates in contact with this drum, printing paper is inserted. Ink inside the printing drum is pushed out to the printing paper through the perforated stencil sheet, whereby ink transfer is performed.
In general, the above-mentioned stencil making apparatus includes reading means 61 which has a line image sensor (hereinafter referred to simply as an image sensor) and stencil making means 62 which has a line thermal print head (hereinafter referred to simply as a thermal head), as shown in FIG. 6. The reading means 61 reads an original 64 being conveyed in the direction of an arrow by a conveyor roller 63 line by line in sequence by an image sensor (a contact type or a reduced optical type) and obtains read data (image data). The read data is sent to an image processing board 65, and image processing is performed. The stencil making means 62 drives the thermal head in accordance with the image-processed data, and a stencil sheet 67 being conveyed in the direction of an arrow by a conveyor roller 66 is perforated by the above-mentioned thermal head. The conveyor rollers 63, 66 are respectively driven to rotate by exclusive drive motors (not shown).
The conventional stencil making apparatus, however, has the disadvantage that conveyor rollers and drive motors both have to be provided two by two and therefore the apparatus increases in size and becomes expensive, since the reading means 61 and the stencil making means 62 are individually provided with the separate conveyor rollers 63, 66 and also the conveyor rollers 63, 66 are respectively provided with exclusive drive motors, as described above.
In addition, because the reading means and the stencil making means convey an original and a stencil sheet by separate drive motors and conveyor rollers, there are cases where there is a difference in speed (difference in an amount of conveyance) between the speed of conveying the original through the reading means and the speed of conveying the stencil sheet through the stencil making means. In such a case, there is a difference between the timing at which data is read from the original and the timing at which the stencil sheet is perforated, and consequently, there is a problem that the stencil sheet cannot be perforated as indicated by the original.
In view of the foregoing observations and description, an object of the present invention is to provide a stencil making apparatus and a stencil making method which are small in size, light in weight and inexpensive by employing single conveying means. Another object of the invention is to provide a stencil making apparatus and a stencil making method in which a difference in timing due to an electric breakdown or surrounding vibrations will not occur between the timing at which data is read from the original and the timing at which the stencil sheet is perforated.
To achieve the aforementioned objects, there is provided a stencil making apparatus comprising
single conveyance means,
reading means which reads an original to obtain data during conveyance of the original, and
stencil making means which perforates a stencil sheet during conveyance of the stencil sheet, based on the data read by the reading means,
wherein the reading means and the stencil making means are juxtaposed on the single conveyance means, and the conveyance of the original to the reading means and the conveyance of the stencil sheet to the stencil making means are performed by the single conveyance means.
The expression xe2x80x9che reading means and the stencil making means are juxtaposed on the single conveyance meansxe2x80x9d is intended to mean that the reading means and the stencil making means are disposed on the single conveyance means so that the conveyance of the original through the reading means during original reading and the conveyance of the stencil sheet through the stencil making means during stencil making can be performed by the single conveyance means.
In the stencil making apparatus, the reading means and the stencil making means are juxtaposed on the single conveyance means, and the conveyance of the original to the reading means and the conveyance of the stencil sheet to the stencil making means are performed by the single conveyance means. With this arrangement, only single conveyance means is required and also only single drive means for driving the conveyance means is required. Accordingly, the size, weight, and cost of the entire apparatus can be reduced.
In the stencil making apparatus, the conveyance means may be a conveyor roller, and the reading means and the stencil making means may be juxtaposed in an axial direction of the conveyor roller.
The xe2x80x9cconveyance meansxe2x80x9d may be any means if it is able to convey an original and a stencil sheet and therefore the conveyance means is not limited to the conveyor roller.
In addition, in the stencil making apparatus, the reading means and the stencil making means may be pushed against the conveyor roller with different pressures, respectively. The reading-means corresponding portion of the conveyor roller which is pushed against the reading means and the stencil-making-means corresponding portion of the conveyor roller which is pushed against the stencil making means may differ in their constituent element, such as material, diameter and the like, in such a manner that the original and the stencil sheet can be conveyed at the same speed.
The expression xe2x80x9cthe original and the stencil sheet can be conveyed at the same speedxe2x80x9d means that a difference in the conveying speed between the two becomes smaller compared with the case where the reading-means corresponding portion and stencil-making-means corresponding portion of the conveyor roller are exactly the same in construction.
Since only one conveyance means is provided, an original and a stencil sheet can be conveyed at the same time by the conveyance means, and original reading and stencil making can be performed at the same time. Therefore, even if a variation in the conveying speed occurs due to an electric breakdown or surrounding vibrations, no difference in speed will occur between the speeds of conveying the original and the stencil sheet and therefore the stencil sheet can be perforated as indicated by the original.
In many cases, the optimum pressures of the reading means and the stencil making means against the conveyor roller differ in order to perform satisfactory original reading and stencil making. The surface of the conveyor roller is usually constituted by an elastic body. If the reading means and the stencil making means are pushed with different pressures, when the conveyor roller is constructed uniformly, the outside diameters of the reading-means corresponding portion and stencil-making-means corresponding portion of the conveyor roller will differ. That is, the contraction amount of the elastic body of the portion pushed with greater pressure is greater. For this reason, the speeds of conveying the original and the stencil sheet differ, and consequently, stencil making will not be synchronized with original reading. However, in the stencil making apparatus of the present invention, a difference between the timing at which stencil making is performed and the timing at which original reading is performed can be reduced, because the outside diameters of the reading-means corresponding portion and stencil-making-means corresponding portion of the conveyor roller differ in constituent element, such as material, diameter and the like, in such a manner that the original and the stencil sheet can be conveyed at the same speed.
In accordance with the present invention, there is a stencil making method comprising the steps of
juxtaposing reading means and stencil making means on single conveyance means,
conveying an original to the reading means and a stencil sheet to the stencil making means at the same time by the single conveyance means,
reading the original to obtain data during the conveyance of the original by the reading means, and
perforating the stencil sheet during the conveyance of the stencil sheet by the stencil making means, based on the data read by the reading means.
Therefore, as with the above-mentioned stencil making apparatus, a difference in the conveying speed between the original and the stencil sheet can be eliminated and the stencil sheet can be perforated as indicated by the original.